Let

x = the money invested in 7% bonds

y = the money invested in 9% bonds

Nancy inherited 600,000 and invested it in bods which pay 7% and 9% simple interest:

x + y = 600,000

The annual interest from the two investments is 49,200:

0.07x + 0.09y = 49,200

By solving the system of equations:

x + y = 600,000

0.07x + 0.09y = 49,200

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x = $240,000

y = $360,000

Nancy invested $240,000 in 7% bonds and $360,000 in 9% bonds.